Anti-theft screw parts are employed, among others, for the theft protection of vehicle wheels. Typically, vehicle manufacturers deliver their vehicles as follows: The wheels are attached via commercially available bolts, mostly hexagon bolts, or there are provided threaded bolts, onto which the wheels are mounted and are fixed with appropriate nuts. Such wheels may be removed by general screw wrenches, i.e. for example, they may be stolen. Specific screw parts have already been known, having a specifically formed head, which only cooperates with a special wrench, i.e. an adapter. Thus, unwanted removal of a wheel may efficiently be interfered.
The anti-theft part of the above-mentioned type is know from DE 199 02 192 A1. In this screw part, several radial recesses starting from the outer circle radially extend outwardly, and forming pockets, into which a wrench may engage. The insert piece is located within an outer circle, within which an inner wall surface of the insert piece is located. The insert piece comprises radially protruding projections. Between the inner circle and the outer circle, a gap annularly extending across 360 degree remains free. Into this annular gap, a tubular tool may be inserted and may be rotated, e.g. with a cordless screwdriver. In doing so, the insert piece may be more and more abraded. In this way, the contribution to encryption locking, which is achieved by the insert piece, may become increasingly reduced. Consequently, it is easier to overcome encryption locking, which essentially is only determined by the outer edge. The different orientation of the insert piece in relation to the piece, and the formation of the insert piece are practically no more essential. A tubular tool will be sufficient that at least has radial recesses, so that it may engage into some of the radial recesses.
With another known screw part according to DE 14 80 817 A1, an annular recess is incorporated into the free end region, and especially is milled thereinto. Said recess having an almost regular contour and uniform width. Such milling is highly complex. Each screw part is required to be individually milled. If it is of desired to not always mill the same recess, the processing machines are required to be readjusted each time. This is highly complex and thus involves appropriately high cost.
Moreover, anti-theft screw parts are know from FR 2 658 253 B1 and U.S. Pat. No. 4,473,169 A.